Canton selectmen will join the opposition to an affordable housing development located mostly in Milton. The buildings in the Milton Mews project, a proposed 276-unit development to be located on Brush Hill Road would be in Milton, but property owned by the developer extends into Canton, according to Canton resident Carl Cummings. Cummings said he would be affected by the traffic caused by the development. “I admit to my own NIMBY,” said Cummings, using the acronym for Not In My Back Yard. “But just because it is in my backyard doesn’t mean I don’t have legitimate concerns.” Selectmen were sympathetic to Cummings’s concerns and had already written a letter to the state Housing Appeals Committee.